Intrinsic Spin Control via Thickness-Vacancy Synergy in 2D Semiconductor for Efficient and Sustainable Photocatalytic Pollutant Removal

Abstract

Intrinsic spin control in two-dimensional (2D) photocatalysts offers a sustainable route for environmental remediation but remains largely unexplored. Herein, a thickness−vacancy synergy strategy was developed to regulate spin density and polarization in g-C3N4 through citric acid-assisted vacancy engineering and thermal exfoliation. The introduction of C vacancies promoted N vacancy formation, while thickness reduction enabled spin polarization at the monolayer limit. The resulting photocatalysts exhibited tunable spin densities that showed a strong positive correlation with pollutant removal performance (R2 = 0.9458). Combined DFT, TRPL, and fs-TA analyses revealed that high spin density suppressed radiative recombination through additional non-radiative pathways, whereas spin polarization enhanced charge separation via spin-selective transfer channels. The optimized catalyst achieved rapid tetracycline degradation (>50% within 5 min) and a 40-fold enhancement in the phenol degradation rate constant. In addition, the system demonstrated low energy consumption, reduced life-cycle impact, and applicability under continuous-flow conditions, complex water matrices, and diverse light sources. This work establishes intrinsic spin engineering as an effective strategy for enhancing photocatalytic pollutant removal and provides a framework for designing high-performance 2D photocatalysts.